You were quiet, intelligent, reserved. Snape favored those types of students, he never had to lecture them but because of their troublesome peers, he felt a bit of remorse for the quiet ones whenever he scolded the whole class.
You were in Professor Snape's last class, which meant that all the kids were both excited to leave, and loud. You only had a few classes with your friends but you wouldn't talk to then much, since they had their own classroom buddy.
It was to say that you, were lonely. You had very little friends but really, people are becoming too selfish and arrogant to even be worthy of your friend. You deserved the best, which was rare to find.
Snape had his favorites, not only from Slytherin but from other houses too, especially Gryffindor. Though, if he had to choose only one, he'd choose you. You were obedient, followed rules, didn't mess up, intelligent, everything that the average high achieving student was.
You'd often hear him giving you small yet dry compliments whenever your potion came out perfect, he'd take a small sample of it and let you keep it whilst he kept one for himself to brag to the class about. It made you feel a little prideful since such a strict teacher would show off his best students' work in a class full of imbeciles.
You had a secret bond with Snape, he was your guardian and he made sure that his best student was safe in any case of danger.